When printing a graphic onto a sheet of work material using known printing devices, the work material is typically advanced through the device in a step-by-step manner with the advancement being momentarily halted between each step. In general, between each step a print-head traverses the work material in a direction perpendicular to the direction of the work material's advancement and transfers a swath of print media such as ink onto the work material in accordance with the graphic being printed. This process is repeated causing successive swaths of ink to be transferred onto the work material immediately adjacent to one another with each pass of the print head.
A problem associated with advancing the work material through the printing device in the above-described step-by-step manner is that the time required to print a graphic can be quite long. This is particularly true where large, and/or complex graphics are concerned. Furthermore, in a production setting, these long print times translate into increased cost, as well as in reductions in printer throughput. Accordingly, there is a present need for printing and plotting devices able to produce graphics in shorter periods of time than is currently possible.
Another difficulty associated with the step-by-step advancement of the work material occurs where the work material is a web fed from a roll. In general, a significant amount of force is required to initiate advancement of the web via rotation of the roll. Similarly, the roll's inertia makes a sudden smooth stop difficult. This sometimes results in the generation of shock pulses in the web of work material which have the potential to detrimentally affect the quality of the graphic being printed.
Based on the foregoing, it is a general object of the present invention to provide an apparatus and method for printing graphics onto work material that overcomes the drawbacks and difficulties associated with prior art devices.
It is a more specific object of the present invention to provide a printing device whereby the advancement of the work material, through the device, and the motion of the print head when traversing and printing on the work material, are synchronized such that the work material is continuously advanced through the device in an uninterrupted motion.